“Twenty sites are currently being evacuated, and more than 10,000 people have been escorted out, though the specific number is still being confirmed,” an emergency services source told news agency Tass.

“This appears to be a case of telephone terrorism, but we have to check the credibility of these messages,” said the source, who noted that the calls began at the same time, and continued after the evacuations had begun.

Among the locations affected are three of the capital’s biggest railway stations, more than a dozen shopping centers – including GUM, located next to Red Square – and at least one university, with unconfirmed reports of evacuation at another.

Tass reported that the railway timetable remained unaffected by the police operation.

An epidemic of hoax bomb warnings has plagued Russia over the past week. Security services told the RIA news agency that over 45,000 people were evacuated from public places in 22 Russian cities on Tuesday, adding that many of the calls appeared to have come from Ukraine.